Irrigation sprinklers for turf and landscaping include spray, impact, and rotor-type sprinklers. The latter are desirable where large areas of uniform coverage are desired. Edwin J. Hunter was the pioneer of gear driven adjustable arc rotor-type sprinklers. Made largely of injection molded plastic parts, a pop-up oscillating rotor-type sprinkler typically includes a riser which telescopes within an outer housing and enclosing a turbine that rotates a nozzle through a gear train and reversing mechanism. The position of one of two arc adjustment tabs or stops can be manually moved, usually with a special tool, to adjust the arc of oscillation. In some cases, an adjustable arc rotor-type sprinkler is equipped with an automatic arc return feature so that the nozzle will resume oscillation between its pre-set arc limits after a vandal has twisted the riser. This prevents watering of sidewalks, patios and other areas besides landscaping, thereby avoiding wasting of water and safety hazards. The nozzle is usually replaceable to achieve the desired trajectory and/or flow rate in gallons per minute. Rotor-type sprinklers used in golf courses often include pneumatically actuated or solenoid-operated valves.